Why do EC2 T2 instances sometimes start with zero CPU Credits

Can anyone explain why when I launch a new T2.micro instance, it occasionally (perhaps 1 in 50) starts with a CPU credit balance of zero, instead of the 30 it is meant to have?

I've attached screenshots of the CPU credit balances from two machines I launched nearly simultaneously from an Autoscaling group.

It isn't a massive deal, but it is upsetting my monitoring system to see near-zero cpu credits!

Solution 1:

Amazon notes in their documentation on T2 (burstable) instances that while these instances normally have 30 CPU credits initially, there are limits to how this initial credit will be applied.

• There are limits to how many T2 instances will launch or start with the initial CPU credit, which by default is set to 100 launches or starts of any T2 instance per account, per 24-hour period, per region. If you'd like to increase this limit, you can file a customer support limit increase request by using the Amazon EC2 Instance Request Form. If your account does not launch or start more than 100 T2 instances in 24 hours, this limit will not affect you.